The present invention relates to a chain conveyor comprising a conveyor belt having a first and a second lateral link chain each one formed by links arranged horizontally and alternating with links arranged vertically, and cross bars connecting the links of one chain to the corresponding links of the other chain, defining the belt conveying plane. Said conveyor belt is driven by belt drive means comprising at least one cogged wheel which engages with the links of one chain and is supported by means of said first and second lateral chains which slide longitudinally along respective first and second longitudinal support guides attached to the conveyor support structure.
In traditional chain conveyors of the type referred above the lateral chains were made to slide on the respective guides by means of horizontal links of the chains.
The longitudinal guides therefore comprised a contact and longitudinal sliding element arranged externally or internally to the chains on which the lower edges of the horizontal links of the chains rested. More specifically, the sliding contact between each chain and the corresponding guide was created by means of the lower edge of the semi-annular portions of the horizontal links projecting from the vertical links towards the exterior of the belt, or by means of the lower edge of the semi-annular portion of the horizontal link projecting from the vertical link towards the inside of the belt respectively.
Such a way of guiding the belt was devised so that the longitudinal guide element, which supported with its upper horizontal face the horizontal links of the corresponding chain, was in direct contact, via its vertical lateral edge, also with the lateral edge of the vertical links of the chain, so as to prevent whatsoever lateral slipping of the belt which was conveyed in this way along a path which was maintained rigidly rectilinear or curved.
Such a guide system was found to be extremely disadvantageous in that in environments where the belt was subjected to heating, such as baking ovens, the expansion of the bars, which pushes the links of the chains outwards, forces guides to be used which support the internal side of the horizontal link. The use of guides on the external side would in fact cause the vertical links to engage against the lateral vertical edge of the guide with a considerable increase in friction. Vice versa, in environments where the system is subjected to cooling, such as refrigerator or freezer rooms, again in order to avoid excessive friction, the shortening of the bars forces the chains to be supported on the external side of the links.
Traditional chain conveyors therefore have limited flexibility of use, it being currently preferable, in order to avoid the disadvantages referred above, to have different guide systems according to whether the conveyor belt is to be used in environments where the system is subjected to heating or to cooling.
If we then take into account the fact that, the horizontal links resting on the guides only with the limited semi-annular portion which projects from the lateral edge of the vertical links, when the guide has not been assembled with good workmanship and for example the distances between opposite sections of the guides are excessive or when work is carried out in environments in which the thermal gradient is considerable and the contraction or expansion of the chain connection bars can be high, a chain may easily fall from the respective guide with derailment of the belt. In order to avoid this occurrence, further elements for lateral restraint of the chain are currently arranged on the side of the chain opposite that of the guide and indirect contact with the chain, these elements normally being assembled in a single part of plastic material with the same guide elements. This forms guide channels which surround a substantial part of the link of the chain which therefore has contacts in a plurality of points with a considerable increase in friction. Said guide channels also have a somewhat elaborate and complex shape and are therefore expensive to manufacture.
Another aspect which must be considered concerns the fact that manufacturing chains of the belt, which are elements with somewhat low manufacturing costs, is carried out approximately by using links which have in fact a certain difference in size one from the other. The integration of the links of one chain with the opposite and corresponding links of the other chain, by means of the cross bars, therefore means that the ends of the bars attached to the chains are not perfectly equidistant one from the other. As a result, in a wholly random and unforeseeable manner, some groups of bars have ends which are therefore closer together on one lateral chain than on the opposite one, while other groups of bars on the contrary have attachment ends which are instead closer together on the other lateral chain. This provides overall a winding course of the belt which, being trapped by the guides in order to move along a path which develops with perfectly rectilinear sections or perfectly curved sections, pushes or pulls the chains against one or the other guide of the chains increasing the friction between said chains and the respective guides.
The problems referred above of traditional guide systems are made even more serious when using the chain conveyor in refrigerator rooms, where the accumulation of ice inside the channel provides further friction and impediments to the sliding of the chain in the channel. Greater friction and hence greater resistance to sliding is also provided by the mere presence of dirt inside the slideways.
The need has also been felt, in order to decrease as far as possible friction between guides and chains, to reduce the reciprocal contact surface which in traditional conveyors is formed at least by the lower faces of the semi-annular portions of the horizontal links.
The use of traditional guide systems in chain conveyors thus involves the need to use large quantities of lubricant which could contaminate the products conveyed with serious disadvantages particularly if food products are conveyed. Their use also involves excessive costs both due to the increased manufacturing cost inherent in the use of drive parts of increased power and as regards the operating costs due to the greater use of energy required for driving the belt as well as obviously due to the fact that excessive quantities of lubricant have to be used.
The object of the present invention is to provide a chain conveyor fitted with a new guide system which eliminates the disadvantages referred above presented by traditional chain conveyor guide systems.
More particularly the present invention sets out to provide a guide system for a chain conveyor which reduces to a minimum friction of sliding with said chains and which makes said conveyor suitable for being used in environments subjected either to heating or cooling and whereby the use of excessive quantities of lubricant and driving power can be avoided.